Hey all - looking for some insight: I bought a house about 3 months ago that has an in-ground concrete/plaster pool and spa combo. The spa has the typical barrier wall w/ overflow configuration where it dumps into the pool while the pump is on or when there is a high bather load. The spa is built so that the water level in it should sit higher (by about 6 inches) than that of the pool, even when everything is sitting idle. My problem is that when the filter cycle completes each morning and the pump turns off, the water level in the spa slowly drops over a few hours until the water level in the spa is even w/ the pool. This exposes a 2 to 3" high band of plaster below the water-line tile and also the top of the first bench.

I know exposing pool plaster for extended periods of time (and letting it bake in the sun all day) is a bad thing, so I've been trying to fix this. So far, I have rebuilt one check valve on the pump discharge to the spa, but this has not remedied the problem. I think it has to be a plumbing issue in conjunction w/ the pool rather than a leak, b/c the water doesn't ever drop below the pool water line. Any thoughts?